ENGINES Pumped and Dumped (NIFE 2025)

What is Bernoulli's equation?

Pt = Ps + 1/2pV^2 -or-

Pt = P + V

Static Pressure produces ___________ energy and can also be referred to as ______________

Potential, Pressure

Dynamic Pressure produces ___________ energy and can also be referred to as ______________

Kinetic, Velocity

Practice your tootsie roll diagram

Practice this diagram for your dump sheet to answer all nozzle/diffuser/convergent/divergent/supersonic/subsonic based questions

What are the three main sections of a Gas Generator?

Compressor

Combustion/Burner Section

Turbine Section

The Brayton Cycle's four events are ______________ _______________ __________________ __________________ and they occur ___________________________, designed for ___________ ______________ engines

Intake, Compression, Combustion, Exhaust

Simultaneously

Gas Turbine

The Otto Cycle's four events are ______________ _______________ __________________ __________________ and they occur ___________________________, designed for _________________________ engines

Intake, Compression, Combustion, Exhaust

Sequentially

Reciprocating

Which type of thrust is based on standard day conditions and is a measurement of thrust solely from velocity of exhaust gases?

Gross Thrust

What is the main purpose of a GTE?

High energy airflow needed to create thrust

What are the three properties that are used in the production of thrust by the GTE?

Pressure, Temperature, Velocity

Which type of thrust is corrected for effects of the inlet airflow velocity?

Net Thrust

Which type of thrust is a more realistic measurement of engines thrust?

Net Thrust

What is the thrust equation?

T = M x A

When are Net and Gross Thrust considered equal?

When inlet airflow velocity = zero and under standard day conditions

Utilizing the TAPERD acronym, what happens to each "letter" to result in an increase in Thrust production?

For better Thrust production:

Temperature: Decreased

Altitude: Decreased

Pressure: Increased

Engine RPM: Increased

RAM: Increased

Density: Increased

Which cockpit instrument is used to indicated pressure of inlet/exhaust airflow and is used in most TJ/TF engines?

Engine Pressure Rato (EPR)

Which cockpit instrument displays shaft horsepower available to drive and for which type of engines?

Torquemeter

TP/TS

Which cockpit instrument provides indication of engine rotation speed (calibrated in percent RPM)?

Tachometer

T/F: The Tachometer measures thrust

False, it does NOT measure thrust

What is the purpose of Inlet Ducts?

Provide proper amount of high pressure/turbulent-free air that is steady/uniform to the first stage compressor

For supersonic inlet ducts, what is another term to describe convergent/divergent shape design that allows for compressible airflow?

Variable Geometry Inlet Duct

T/F: Supersonic is compressible while Subsonic is incompressible

True

Supplying enough air to satisfy combustion is the main purpose of what section in the GTE?

Compressor

What are the three types of Compressors?

Centrifugal

Axial

Axial-Centrifugal

What are the three main components of a Centrifugal Flow Compressor and what do they do?

Impeller (aka Rotor inducer)

- Increases the total pressure of the air and sent to the diffuser through a divergent passage

Diffuser:

- Converts high velocity air flow from the impeller to high pressure, decreasing velocity and increasing pressure

- "Point of highest compression"

- Divergent design

Manifold:

- Routes high pressure air to combustion

Which compressor is rugged, low cost, good power output over large range of RPMs and has high pressure increase per stage of compression?

Centrifugal Flow Compressor

Which compressor requires a large front area and is impracticable for multiple stages?

Centrifugal Flow Compressor

Which compressor provides a straight line flow of air through the compressor?

Axial Flow Compressor

What are the 2 main elements of the Axial Flow Compressor in the correct order?

Rotor -> Stator

T/F: Because of the multiple stages of rotor/stator in a Axial Flow Compressor, they have great compression ratios with efficiencies near 90%

True

What are the two types of spools of the Axial Flow Compressor?

Single Spool Axial Flow Compressor

Dual Spool Axial Flow Compressor

The Low pressure turbine drives the ____ _______ __________ while the High pressure turbine drives the ____ _______ ________________________________ in a dual spool axial compressor

Low Pressure Compressor

High Pressure Compressor

What is the OHIO acronym regarding?

Dual Spool Axial Flow order

O = "LOw" pressure compressor -->

H = "High" pressure compressor -->

I = "hIgh" pressure turbine -->

O = "LOw" pressure turbine

Which compressor has a high combustion efficiency due to multiple stages but is high cost and has a higher chance to have compressor stalls at low airspeeds?

Axial Flow Compressors

For Axial-Centrifugal Flow compressors, what is provided by the "Axial" portion and what is provided by the "Centrifugal" portion that makes it a hybrid compressor?

Axial: Straight through RAM efficiency and multiple stages for high pressure

Centrifugal: Significantly increases pressure per stage

Which compressor provides large pressure increase for engine size suited for smaller mission aircraft but not suited for supersonic airflow?

Axial Centrifugal Flow Compressors

Which guide vane impart a swirling motion to the air entering the compressor in the direction of the engine/compressor rotation and directs flow to first stage rotor?

Inlet Guide Vane

Which guide vane is known as the straightening vane and are at the last set of stators which prepare airflow for the diffuser?

Exit Guide Vane

Which guide vane reduces airflow turbulence caused by rotational movement of the compressor?

Exit Guide Vane

Where is the diffuser located within the GTE?

After the compressor but before the combustion chamber

Which section in a GTE provides proper mixing of Fuel and Air for proper combustion?

Combustion/Burner Section

The combustion section adds _____ energy to accelerate gases to produce ________

Heat, Thrust

Primary air is ____% of the airflow from diffuser mixed with _______ within the _______________________ for ignition

25%

fuel

combustion chamber

Secondary air is ___% of the airflow that flows around the _____________________ ___________ to provide what three things?

75%

combustion chamber

1. cooling the thin walls

2. control the flame

3. afterburner operations

When designing a combustion chamber, what four goals should be followed?

M.F.C.B (My Flame Can't Blow-out)

1. Minimize Pressure Decrease

2. Flame must not blow out

3. Combustion efficiency must remain high

4. Burning must be complete before entering turbine section

What are the three types of Combustion Chambers?

Can

Annular

Can Annular

Which type of combustion chamber is used on older centrifugal compressor engines and can contain its own fuel nozzle, burner lining, and casing?

Can Combustion Chamber

Which combustion chamber is known for its strength, durability, and ease of maintenance but has greater pressure loss and results in cold spots on turbine?

Can Combustion Chamber

Which combustion chamber is known for its uniform heat distribution across the face of the turbine section, better use of space, and provides better mixing of fuel/air

Annular Combustion Chamber

Which combustion chamber results in a engine overhaul if maintenance is required?

Annular

Which combustion chamber is known for its ease of maintenance with good thermodynamics, lower pressure loss, used on high performance aircraft but is expensive?

Can Annular

The turbine section transforms ____% of ____ energy of expanding gases from the ______________________ ___________ into ____________________ energy to drive the compressor and accessory gear box

75%

heat

combustion chamber

mechanical energy

What is the order of the rotors/stators for the Turbine Section?

Stator ---> Rotor

______ % of heat energy is turned into mechanical energy while ____% is used for thrust by the Turbine Section of a GTE

75%

25%

What section is the highest stressed section of the GTE?

Turbine Section, operating at 2000 degrees F

Excessive heat/high temp of the turbine can cause blades to "___________" which a ______ _______ attachment can help prevent/decrease the risk of this

Creep

Fir Tree

Which section of a GTE is responsible to direct the flow of hot gases rearward, causing high exit velocity of gases while preventing turbulence?

Exhaust Section

What are the three parts of the Exhaust Section?

Exhaust Outer Duct

Exhaust Inner Duct

Radial Hollow Struts

What are the two kinds of exhaust nozzles?

Convergent

Convergent-Divergent (aka Variable Exhaust Nozzle)

What type of nozzle is used for supersonic aircraft?

Convergent-Divergent/Variable Exhaust Nozzle

T/F: Primary air from the burner section is used to support Afterburner operations

False, Secondary Air is used for AB Ops

What are the three ways that afterburners can be ignited by?

Spark Ignition (most common)

Torch Ignition (Pilot Light)

Hot Stream Ignition

Afterburner assembly consists of what 4 components?

Spray Bars

Screech Liner

Flame Holder

Variable Exhaust Nozzle

Which component of the Afterburner introduces fuel to afterburner?

Spray Bars

Which component of the afterburner helps in mixing fuel and air?

Flame Holder

Shock absorber in the Afterburner section is called the:

Screen Liner

Turkey Feathers is another name for the ________ __________ _____________ which is used for afterburner operations

Variable Exhaust Nozzle

Basic components of the reciprocating engine?

4 C's, 2 V's, 1 P

The angle between the relative wind and rotor blade's chord line makes up what?

Angle of Attack for a compressor

What is formed within the compressor by combining inlet airflow and the compressor RPM?

Relative wind

Any change to inlet airflow or compressor RPM (will or will not) change the Relative wind?

will

Anything that decreases the inlet airflow or increases compressor RPM will increase the ______ and increase the possibility of a ________________ _______

AOA

Compressor Stall

Indications of a compressor stall include:

Mild pulsations

Engine Vibration with Noise (Popping/Banging)

ITT increase

RPM decay

Fluctuating gauges

Compressor stalls are a result of _____________________________ or ____________________________________

Airflow Distortion

Mechanical Malfunctions

What are the four mechanical malfunctions that can lead to a compressor stall?

V2F2

Variable Inlet Guide Vane/Stator Vane Failure

Variable Exhaust Nozzle Failure

FCU Failure

FOD

Pilots can reduce the possibility of a compressor stall by avoiding what 4 actions?

Avoiding "F.A.M.E"

1. Flight through severe weather/turbulence

2. Abrupt attitude changes

3. Maintain prescribed minimums

4. Erratic or abrupt PCL movement

What are the four engine designs to minimize chance of compressor stall?

1. Variable Inlet Guide Vane/Stator Vane

- Note this is positioned by the stator vane actuator via FCU

2. Dual Spool Axial Flow Compressors

3. Bleed Valves

4. Variable Exhaust Nozzles

Of the two, which is the most common cause of compressor stall?

Airflow distortion

What are the 4 airflow distortions that can cause a compressor stall?

Caused by D.A.R.E

Deficiency of air velocity/volume caused by atmospheric conditions

Abrupt attitude change

Rapid Throttle Movement

Encountering Air Turbulence

How can you recover from a compressor stall?

Decrease inlet AOA by reducing attitude to allow engine to catch up with the inlet airflow

What is defined as the amount of fuel required to produce one pound of thrust?

Thrust Specific Fuel Consumption (TSFC)

Create the Engine Thrust/TSFC Chart

Practice this for your dump sheet

The Turbo____ engine is the simplest form of GTE consisting of an ________________ & ______________ section

Turbojet

Inlet

Exhaust

The Turbo________ has a high TSFC at low altitude/airspeeds and has the lightest specific weight per pound of thrust produced?

Turbojets

For a Turbofan, the fan is driven by which section of the GTE?

Turbine section

What is the exhaust and mechanical percentage of thrust produced in a Turbojet?

Exhaust: 100%

Mechanical: 0%

Amount of air that bypasses the gas generator compared to the amount of air that passes through the gas generator is called what?

Bypass Ratio

Most fuel-efficient aircraft have a (higher or lower) bypass ratio, which yield a lower TSFC

Higher

The turbo_____ push large mass of air, increasing thrust

Turbofan

What is the thrust percentages for a Turbofan (both low bypass and high bypass)?

Low Bypass TF:

Exhaust: 70%

Mech: 30%

High Bypass TF:

Exhaust: 40%

Mech: 60%

The turbo_____ has higher thrust at low airspeed but less efficient at higher altitudes with a higher specific weight?

Turbofan

The Turbo_____ imparts a small amount of acceleration to a large mass of air?

Turboprop

The propeller assembly, reduction gear box, torquemeter assembly, and propeller are all components of the Turbo______

Turboprop

What provides majority of thrust for the Turboprop, yielding a ____% as mechanical and ____% as exhaust?

The Propeller

90%

10%

What is hydraulically controlled, constant speed, full feathering, and reversible regarding Turboprops?

Propeller Assembly

What are the three main components of the Propeller Assembly of a Turboprop and which one changes blade angle of propeller?

Blade Assembly

Hub Assembly

Pitch Change/Dome Assembly (changes blade angle)

The Reduction Gear Box (RGB) converts ________ RPM and ________ Torque into _______ RPM and _________ Torque necessary for efficient propeller operation

High, Low, Low, High

The RGB prevents what in a turboprop engine?

Prevents blades reaching supersonic speeds

What assembly of the Turboprop Engine is a set of shafts located between the gas generator and reduction gear box?

Torquemeter Assembly

What is connected to the RGB and GTE to transmit and measure the power output from the GTE to the RGB

Torquemeter Assembly